Method and apparatus for remote self-propelled conveying in mineral deposits

ABSTRACT

A method and apparatus for the mining of material from a seam includes a mining apparatus and a self-propelled conveyor capable of advancing or retreating in the seam on its own power and an advancing and steering arrangement for the mining apparatus. The self-propelled conveyor, electric cables and other services for the mining apparatus are protected against roof falls. The power input for the self-propelled conveyor is provided by continuous drive shafts powered at either one or both ends of the conveyor. Alternately, a unique reciprocating conveyor mechanically powered at either one or both ends of the conveyor is provided for conveying of aggregate material. An apparatus for assembling the conveyor and receiving aggregate material is provided at the rear end of the conveyor. A method and apparatus for accurately and precisely navigating the mining machine is disclosed.

[0001] This application is a Continuation-In-Part of U.S. patentapplication Ser. No. 09/250,689, filed Feb. 16, 1999.

FIELD OF THE INVENTION

[0002] The present invention relates generally to mining andspecifically to conveying in remote mining of bedded mineral deposits.

BACKGROUND OF THE INVENTION

[0003] Known methods of remote mining in bedded mineral deposits such ascoal seams employ a mining machine that excavates mine openings to somedistance from the seam exposure on the surface and means of conveyingare required to transport the excavated material to the surface. In mostof the present systems, conveying machines consisting of multipleconveyors are advanced into the mine openings from the surface. Forexample, U.S. Pat. Nos. 5,112,111, 5,232,269 and 5,261,729 to Addingtonat al. disclose an assembly of conveyors and a mining machine advancedinto the seam without interrupting the flow of aggregate material byseparate means designed to pull at the forward end and push at therearward end. Similarly, U.S. Pat. No. 5,609,397 to Marshall at al.discloses an assembly of conveyors interconnected with a mining machineand a driving device located outside the seam and consisting of rack andpinion or, alternately, reciprocating cylinders, linear tracks, linearor rotary drives, chains, cables or other mechanical devices. The U.S.Pat. No. 5,692,807 to Zimmerman discloses a guidance assembly forextending and retracting an assembly of conveyors in and out of theseam. The U.S. Pat. No. 3,497,055 to Oslakovic at al. discloses amulti-unit train of conveyors having a self-propelled unit at each endcoupled to intermediate units, each end unit being capable of towing theintermediate units. The U.S. Pat. No. 2,826,402 to Alspaugh at al.discloses a train of wheeled conveyor sections pulled into the mineopening and pushed out of it by a self-propelled mining machine.Buckling of the train is avoided by the grooves made by the miningmachine in the floor, said grooves spaced the same distance as thetreads of the wheels carrying the conveyor sections.

[0004] At present, as the interconnected combination of the miningmachine and a conveying assembly comprising a plurality of conveyors isadvanced some distance into the seam from a launch vehicle located onthe outside, the axial force within the combination becomes excessivewith respect to its length and the combination becomes less rigid. As aconsequence, it becomes difficult to steer the mining machine located atthe front of the combination and the conveying assembly itself canbecome unstable, which limits the penetration depth of mining.Furthermore, pulling the conveying assembly at the rearward end when itbecomes entrapped by a rock fall may sometimes cause the conveyingassembly to brake. It would therefore be desirable to provide foradvancing and withdrawing the conveying assembly while minimizing theaxial force within the conveying assembly.

[0005] Where the conveying assembly consists of a plurality of conveyorunits, each of the individual conveyors requires a separate input ofelectric power which, in turn, requires coupling and uncoupling ofelectrical cables as the assembly is advanced into or retracted from themine opening. It would be therefore desirable to provide a power inputthat does not require electric power at each individual conveyor of theassembly.

[0006] If the electric power input is not provided at each individualconveyor, the conveying assembly cannot be extended withoutinterruption, as claimed in the U.S. Pat. No. 5,112,111 to Addington atal. It would therefore be desirable to provide for extending theconveying assembly while minimizing the time required for such extensionof the machine.

[0007] Where open conveyors are used, they are prone to damage by fallsof rock from unsupported roof. Often, when rock falls occur, mining mustbe interrupted and the conveying assembly brought to the surface inorder to remove fallen rock from the machine and to repair damage. Itwould therefore be desirable to provide a conveying assembly that isenclosed in a protective enclosure and that is capable of withstandingat least moderate rock falls.

[0008] Electric cables, control cables and hoses for the remote miningmachine that lay atop the conveying assembly are also prone to damage byrock falls. It would therefore be desirable to provide protectiveenclosures for cables, hoses and other services provided for the remotemining machine.

[0009] A remote mining machine located at the forward end of theconveying assembly may become entrapped by fallen rock and the tractionforce of the conveying assembly may not be sufficient to extract themining machine. It would therefore be desirable to provide independentmeans of extracting the mining machine from the seam.

[0010] One type of mining for which the present invention is intended tobe used is highwall mining. With highwall mining, the mining machinepenetrates a substantially vertical face containing a seam. The miningmachine digs into the face substantially perpendicularly thereto. Toensure the structural integrity of the mine is maintained, pillars ofunmined material are left between the holes dug by the mining machine.These pillars support the roof and are therefore essential to avoiding arock fall. Those of ordinary skill in the art will understand that inorder to maintain minimum acceptable pillar thickness, it is desirableto dig exactly perpendicularly to the face. Any angular deviation by themining machine as it travels requires an increased initial pillar width,which decreases the amount of material that can be removed from themine. Therefore it is desirable to maintain accurate and preciseknowledge of where the mining machine is located. Likewise, it isdesirable to navigate the mining machine precisely and accurately to adesired location. In this manner, the operator can ensure that thedesired mining path is followed.

[0011] One known method of determining mining machine position employs asystem of gyros and accelerometers to estimate the distance traveled bythe mining machine. This type of known method uses complicated softwarethat requires several minutes to initiate during which the miningmachine cannot be moved. The method also requires periodicre-calibration during use, which also requires the mining machine be atrest. Furthermore, this system is expensive, costing more than $100,000.Thus, what is needed is a cost-efficient mining machine that canaccurately and precisely determine the position of the mining machinehead.

SUMMARY OF THE INVENTION

[0012] Accordingly, it is an object of the present invention to providea method and apparatus for advancing a remote conveying assembly withoutcausing excessive axial forces within the assembly, by providingtractive forces at multiple locations along the length of the assembly.

[0013] Another object of the present invention is to provide a methodand apparatus for remote conveying that does not require electric powerat each conveying section of the conveying assembly.

[0014] Another object of the present invention is to provide a methodand apparatus for extending the conveying assembly that minimizes thetime required for extensions.

[0015] Another object of the present invention is to provide a methodand apparatus for protecting the remote conveying assembly, electriccables and other services from damage by rock falls.

[0016] Another object of the present invention is to provide a methodand apparatus for advancing and steering the remote mining machineindependently of advancing the conveying assembly.

[0017] Another object of the present invention is to provide a methodand apparatus for accurately and precisely determining the position ofthe mining machine within the seam.

[0018] These and other objects of the present invention will becomeclear from the detailed description of the invention, the drawings, andthe claims included below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention is described with reference to theaccompanying drawings, in which like reference characters reference likeelements, and wherein:

[0020]FIG. 1 is a schematic side view of the first part of the preferredembodiment of the present invention located outside the seam, includinga mining platform, stacker and a rearward end of the conveying assembly;

[0021]FIG. 1A is a schematic side view of the assembly in FIG. 1,showing the conveying assembly advancing into the seam;

[0022]FIG. 2 is a schematic plan view taken along line I-I of FIG. 1;

[0023]FIG. 2A is a schematic plan view taken along line I-I of FIG. 1A;

[0024]FIG. 3 is a schematic side view of the second part of thepreferred embodiment of the present invention, located inside the seam,including a forward end of the conveying assembly, feeder/breaker,extender, bracer and a mining machine;

[0025]FIG. 3A is a schematic side view of the second part of thepreferred embodiment of the present invention, showing the bracer andthe extender located on a separate advancing machine independent of thereceiving module;

[0026]FIG. 4 is a schematic plan view taken along line II-II of FIG. 3;

[0027]FIG. 4A is a schematic plan view taken along line II-II of FIG. 3,showing the extender extended and the mining machine advanced ahead ofthe conveying assembly;

[0028]FIG. 4B is a schematic plan view taken along line X-X of FIG. 3A;

[0029]FIG. 5 is a schematic side view of a component of the conveyingassembly utilizing belt conveyors;

[0030]FIG. 6 is a schematic plan view taken along line III-III of FIG.5;

[0031]FIG. 7 is a schematic sectional view taken along line IV-IV ofFIG. 6;

[0032]FIG. 8 is a schematic sectional view taken along line V-V of FIG.6;

[0033]FIG. 9 is a schematic sectional view similar to FIG. 8, utilizingchain conveyors;

[0034]FIG. 10 is a schematic side view of a component of the conveyingassembly utilizing a reciprocating conveyor;

[0035]FIG. 11 is a schematic plan view taken along line VI-VI of FIG.10;

[0036]FIG. 12 is a schematic sectional view taken along line VII-VII ofFIG. 10, of a preferred embodiment of reciprocating conveyor utilizingpush plates;

[0037]FIG. 13 is a schematic sectional view taken along line VIII-VIIIof FIG. 11, of a preferred embodiment of reciprocating conveyorutilizing push plates, with push plates in a rearward motion;

[0038]FIG. 14 is a schematic sectional view taken along line VIII-VIIIof FIG. 11, of a preferred embodiment of reciprocating conveyorutilizing push plates, with push plates in a forward motion;

[0039]FIG. 15 is a schematic cross sectional view of another embodimentof reciprocating conveyor utilizing push plates, with push plates in arearward motion;

[0040]FIG. 16 is a schematic sectional view of another embodiment ofreciprocating conveyor utilizing push plates, with push plates in arearward motion;

[0041]FIG. 17 is a schematic sectional view of another embodiment ofreciprocating conveyor utilizing push plates, with push plates in aforward motion;

[0042]FIG. 18 is a schematic sectional view of yet another embodiment ofreciprocating conveyor utilizing push plates, with push plates in arearward motion;

[0043]FIG. 19 is a schematic sectional view of yet another embodiment ofreciprocating conveyor utilizing push plates, with push plates in aforward motion;

[0044]FIG. 20 is a plan view of another embodiment of the advancingmachine including a navigation system for a remote operation, with theextender retracted;

[0045]FIG. 21 is a plan view of the advancing machine with a navigationsystem, with the extender extended;

[0046]FIG. 22 is a side view of a preferred embodiment of theintermediate module with couplings engaged to connect the intermediatemodules;

[0047]FIG. 23 is a side view of a preferred embodiment of theintermediate module with couplings disengaged to disconnect theintermediate modules;

[0048]FIG. 24 is a schematic sectional view taken along line A-A of FIG.22;

[0049]FIG. 25 is a side view of a coupling assembly of the embodiment ofFIG. 22; and

[0050]FIG. 26 shows an alternate embodiment of the platform of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] Referring to FIGS. 1 through 8, a remote mining machine 1excavates material in the mine opening 2 within a seam 3. Opening 2could also be a tunnel opening. The mining machine 1 discharges theexcavated material onto the receiving module 4 of the self-propelledconveying assembly 5. The self-propelled conveying assembly 5 consistsof the receiving module 4, a plurality of intermediate modules 6 and adrive module 7. The mining machine 1 is connected to the receivingmodule 4 with extenders 12, shown in the drawings as advancingcylinders, which are used to advance the mining machine 1 into themining room 2 and also to directionally steer it. Advancing cylinders 12can steer the mining machine 1 by extending in different amounts or atdifferent rates on either side of the mining machine 1. The receivingmodule 4 also carries braces 8. Bracers 8 typically take the form ofside jacks and are normally used for steering the receiving module 4within the mine opening 2. However, if the mining machine 1 is trappedby a rock fall, the side jacks 8 are braced between the walls 9 of themine opening 2 and cylinders 12 are used to extract the mining machine 1from under the rock fall. Alternatively, the jacks 8 can be bracedbetween the roof and floor of the mine opening 2. Where necessary, thereceiving module 4 carries a feeder 10 and a breaker 11.

[0052] Referring to FIGS. 3A and 4B, in an alternate embodiment,advancing cylinders 12 and side jacks 8 are mounted on an advancingmachine 4 a separate from the receiving module 4. The advancingcylinders 12 of the machine 4 a are connected to the mining machine 1.The receiving module 4 is not fixedly connected to the advancing machine4 a and the receiving module 4 with the self-propelled conveyingassembly 5 can advance into the mine opening 2 independently of themining machine 1 and the advancing machine 4 a.

[0053] A very important aspect of this invention is the manner in whichthe self-propelled conveying assembly 5 advances into the mine opening 2excavated by the mining machine 1. Unlike other systems currently inuse, all modules of the conveying assembly 5, including all theintermediate modules 6 and the receiving module 4, have one or morepropelling devices 13—driven axles with wheels are shown in the figures.The driven axles 13 are capable of generating a traction force to propelthe conveying assembly either forward or backward. Driven axles 13receive power from one or more drive shafts 14 driven from the drivemodule 7 located on the mining platform 15, through drives 16. As allthe driven axles 13 are interconnected through the drive shafts 14, theyare forced to advance or retreat at the same speed, regardless of thetorque they may require. The whole conveying assembly 5 advances orretreats at the same speed without any appreciable push or pull withinthe conveying assembly 5, thus assuring a uniform and problem-freeadvance or retreat.

[0054] In a preferred embodiment of the present invention, individualconveyors 17 mounted within the intermediate modules 6 and the feeder 10of the receiving module 4 also receive power from at least one driveshaft 18, which is driven from the drive module 7 located on the miningplatform 15, through drives 19. Alternatively, individual drives, suchas electric motors, located on modules 6 can be used to power modules 4,6 and/or conveyors 17 and/or feeder 10.

[0055] The drive module 7 includes tram power drives 20 that power thedrive shafts 14 and conveyor power drives 21 that power the drive shafts18. FIG. 1a shows drives 20, 21 located on the same level as theintermediate module 6. Alternatively, drives 20, 21 can be positionedabove module 6, as seen in FIG. 26. In this latter embodiment, drives20, 21 are movably positioned on rails above module 6. This embodimentprovides additional working space on platform 15.

[0056] During the advancing or retrieval operation, all components ofthe conveying assembly 5, including the drive module 7, the intermediatemodules 6 and the receiving module 4, are coupled together by couplings22 while the drive shafts 14 are coupled together by drive couplings 23and drive shafts 18 are coupled by drive couplings 24. When theintermediate modules 6 are coupled, the head ends 25 and the tail ends25A of the conveyors 17 overlap in order to facilitate transfer of thematerial 26.

[0057] The mining platform 15 includes a discharge conveyor 27, thedrive module 7, cable and hose winders 28, winches 29, a control room30, an electrical room 31, a retractable ramp 32, and other requiredequipment and facilities. The retractable ramp 32 accommodates theelevation difference between the bottom deck 33 of the platform 15 andthe bottom 34 of the seam 3. Tracks 35 or other modes of transportationare provided to facilitate positioning of the mining platform 15 withrespect to the mine opening 2.

[0058] An important aspect of this invention is the method and apparatusof adding intermediate modules 6 to the conveying assembly 5. Theextended bottom deck 33 includes a sliding table 36. Cargo handlingequipment such as a commonly available forklift or a front-end loader isused to deposit an intermediate module 6 onto the sliding table 36. Whenthe conveying assembly 5 advances into the mine opening 2 a full lengthof one intermediate module 6, the drive module 7 is disconnected fromthe last rearward intermediate module 6 and moved toward the dischargeend 37 of the discharge conveyor 27, by a moving mechanism 38 attachedto the drive module 7, thus generating a gap in the conveying assembly 5that is greater than the length of an intermediate module 6. The slidingtable 36 with an intermediate module 6 is moved sideways until theintermediate module 6 is lined up with the conveying assembly 5 at whichpoint the drive module 7 is moved toward the new intermediate module 6and all the components of the conveying assembly 5 are reconnected. Asthe drive shafts 14 and 19 are also reconnected through couplings 23 and24, all axles 13 and conveyors 17 are powered and begin operating.

[0059] The intermediate modules 6 contain protective plates 39, 40 and41 in order to protect mechanical and electrical components of theconveying assembly 5, including conveyor 17, electrical cables 42 andhoses 43. For this purpose, the electrical cables 42 and the hoses 43are laid into structural trays 44. The sides 45 of the structural trays44 also perform a function of guiding the conveying assembly 5 withinthe walls 9 of the mine opening 2.

[0060] Referring to FIG. 9, chain conveyors 46 are mounted within theintermediate modules 6. The chain 47 includes flights 48 that swingdownwards by gravity when they travel in the direction of transportshown by an arrow 49 and push the aggregate or other material 50 withinthe intermediate module 6. In order to make the conveyors 46 more spaceefficient, a cam 51 swings the flights 48 to a horizontal positionduring their return path shown by an arrow 52.

[0061]FIGS. 10 through 14 show a schematic of the intermediate modules 6with a reciprocating conveyor 53. Each module 6 contains a section 54 ofa reciprocating conveyor 53. Each section 54 contains flights 55 withtransverse shafts 56, rollers 57 that run in guides 58, supportingrollers 59 and a longitudinal shaft 60. The shafts 60 of sections 54 areconnected by couplings 61 and form a single shaft connected to areciprocating mechanism mounted on the drive module 7 located on themining platform 15. When the flights 55 are moved in the direction oftransport designated by an arrow 62, they swing into a substantiallyvertical position and push the material 50 within the intermediatemodule 6 in the direction of transport. When the flights 55 are moved inthe opposite direction, they swing into a substantially horizontalposition by the resistance of the material 26 and return without pushingthe material 50.

[0062]FIGS. 15 through 17 show a schematic of the intermediate modules 6with another embodiment of a reciprocating conveyor 62 containingflights 63 with rollers 64 that run in guides 65 within longitudinallinkages 66. When the flights 63 are moved in the direction of transportdesignated by an arrow 67, they swing into a substantially verticalposition and push the material 50 within the intermediate module 6 inthe direction of transport. When the flights 63 are moved in theopposite direction, they swing into a substantially horizontal positionby the resistance of the material 50 and return without pushing thematerial 50.

[0063]FIGS. 18 and 19 show a schematic of the intermediate modules 6with yet another embodiment of a reciprocating conveyor. In thisembodiment, flights 68 are moved into a substantially vertical positionwhen moving in the direction of transport and into a substantiallyhorizontal position when moving in an opposite direction by cams 69moving within guides 70.

[0064] Referring to FIGS. 20 and 21, in an alternate embodiment, theadvancing module 4 a with advancing cylinders 12 and side jacks 8 alsocontains secondary braces, in the form of side jacks, 101 and distancemeasuring means 103, 104 and 105 with readout instruments 102. Beforethe mining machine 1 is advanced and steered within the mine opening 2via advancing cylinders 12, the distance measuring means 103, 104 and105 are used to record distances OM, ON, and NP. Since the distances MNand OP are fixed, the relative positions of points M, N, O and P can bedetermined by triangulation (using the cosine and sine theorems providedbelow). This also determines the relative position of the advancingmachine 4 a and the mining machine 1. When the mining machine 1 isadvanced to a new position within the mine opening 2, the secondary sidejacks 101 are extended, the mining machine 1 is fixed within mineopening 2, the new distances OM1, ON1 and NP1 are measured and the newpositions of points M and N are determined relative to points O and P.Next, the side jacks 8 are released and cylinders 12 are retracted. Whenthe cylinders 12 are fully retracted, the side jacks 8 are extended,again fixing the advancing module 4 a within the opening 2, and thedistances OM, ON, and NP are measured. The new position of points O andP relative to points M and N are determined as before. By repeating thiscycle, the position of mining machine 1 as it is advanced within themine opening 2 is determined at regular intervals and, accordingly, themining machine 1 is steered by advancing cylinders 12 to maintain thedesired direction of mining. Advancing machine 4 a may also contain oneor more inclinometers to measure vertical displacement (if any) ofmining machine 1. The inclinometers are contained within advancingmachine 4 a with distance measuring means 103, 104, 105. Employinginclinometers allows for the calculation of the absolute position ofmining machine 1 in three-dimensional space. This may be desirable ifthe mining machine 1 is being operated within an inclined seam.

[0065] Given three sides of any triangle, the angles can be determinedfrom cosine and sine theorems as follows: $\begin{matrix}{{Cosine}\quad {{Theorem}:}} & {{\cos \quad \alpha} = \frac{b^{2} + c^{2} - a^{2}}{2{bc}}} \\{{Sine}\quad {{Theorem}:}} & {{\sin \quad \beta} = \frac{b\quad \sin \quad \alpha}{a}} \\\quad & {{\gamma = {{180{^\circ}} - \left( {\alpha + \beta} \right)}},}\end{matrix}$

[0066] where in the first triangle (MNO): a=MN, b=OM, c=ON, α=

MON, β=

MNO, and γ=

OMN; and in the second triangle (NOP): a=OP, b=NP, c=ON, α=

ONP, β=

NOP, and γ=

OPN.

[0067] The navigation procedure is as follows:

[0068] Step 1: Stabilize O and P with side jacks 8 and move M and N withadvancing cylinders 12. OM changes to OM1, ON to ON1, and NP to NP1. MNand OP remain fixed.

[0069] Step 2: Stabilize M and N with secondary jacks 101 and calculatenew coordinates of M and N by triangulation.

[0070] Step 3: Release side jacks 8 and move O and P with advancingcylinders 12. OM1 changes to OM2, ON1 to ON2, and NP1 to NP2. MN and OPremain fixed.

[0071] Step 4: Stabilize O and P and calculate new coordinates of O andP by triangulation.

[0072] Repeat steps 1 through 4.

[0073] The above process measures actual distance traveled, rather thanestimating it. Thus it allows the user to calculate the instantaneousposition of mining machine 1 to an accuracy not obtainable with knownposition measuring means for mining machines. This allows the user tocalculate the actual azimuth of the mining machine, in turn allowing formaximum material extraction from the mine. Using the above process tomove mining machine 1 a distance of 1500 feet, while employingcommercially available measuring means, will result in a positioncalculation that is accurate within three inches (0.167% error).Furthermore, the lack of complex measuring devices makes the presentinvention more reliable and less expensive than known apparatus.

[0074] Distance measuring means 103, 104, and 105 can take many forms.In the preferred embodiment, rotary potentiometers are used. Cables areattached between the points M, N, O, and P. As points M and O moverelative to points N and P, the cables modify the potentiometers. Bycomparing the measurements before and after the modifications, thepotentiometers can measure the amount and direction of movement. Otherpossible embodiments for the measuring means 103, 104, and 105 compriselinear potentiometers, proximity sensors, lasers, ultrasonic equipment,infrared sensors, hydraulic or pneumatic cylinders, and other knowndistance measuring apparatus.

[0075] Referring to FIGS. 1, 2, and 22 through 25, an endless beltconveyer 17 is mounted in an intermediate module 6. Drive shaft 14powers axles 13 through drives 16 and drive shaft 18 powers the conveyer17 through drives 19. In order to add an intermediate module 6 to aconveying assembly 5, said intermediate module is advanced toward theconveying assembly 5. Cam 77 located on the bottom deck 33 of theplatform 15 engages roller 75 and the raised portion 78 of the cam 77raises roller 75 mounted on the hook 72. This causes the hook 72 torotate around the pin 73 and clear the pin 76. The hook 72 then entersthe fork 80 in the plate 71 of the coupling assembly 22. As theintermediate module 6 advances with the conveying assembly 5 toward themine opening 2, roller 75 is disengaged from the cam 77 and hook 72,under the force of gravity, engages the pin 76, locking it within thefork 80. A spring can also be used to bias the position of hook 72.Stopper 74 holds the hook 72 in the lowermost position. While thecoupling assemblies 22 engage intermediate modules 6 with one another,couplings 23 and 24 connect drive shafts 14 and 18. As can be seen fromFIG. 25, couplings 23 and 24 together with flexible couplings 79 arecapable of accommodating variable grades of the floor 2A in the mineopening 2. The rotation about the transverse axis between intermediatemodules 6 occur around the pin 76, while the hook 72 rotates about thepin 73. A limited rotation about the longitudinal axis is allowed due tothe clearance between the fork 80 and the pin 76.

[0076] To remove intermediate module 6 from the conveying assembly 5,the operation is reversed. As the conveying assembly 5 trams out of themine opening 2, raised portion 78 of the cam 77 lifts roller 75 androtates hook 72 away from pin 76. The disengaged intermediate module 6continues tramming onto the bottom deck 33 while the rest of theconveying assembly 5 remains stationary, in order to separate thedisengaged intermediate module from the conveying assembly.

[0077] While the preferred embodiments of the present invention havebeen described above, it should be understood that they have beenpresented by way of example only, and not of limitation. It will beapparent to persons skilled in the relevant art that various changes inform and detail can be made therein without departing from the spiritand scope of the invention. Thus the present invention should not belimited by the above-described exemplary embodiments, but should bedefined only in accordance with the following claims and theirequivalents.

What is claimed is:
 1. A method of advancing a mining machine including an advancing machine, comprising: bracing the advancing machine within a mine opening; moving the mining machine away from the advancing machine; releasing the advancing machine; and moving the advancing machine toward the mining machine.
 2. A method according to claim 1 , wherein said bracing includes bracing the advancing machine between a roof and a floor of said mine opening.
 3. A method according to claim 1 , wherein said bracing includes bracing the advancing machine between walls of said mine opening.
 4. A method of steering a mining machine having a plurality of sides and having an advancing machine operatively connected thereto, comprising: bracing the advancing machine within a mine opening; and increasing a distance between the advancing machine and the mining machine by different amounts on two of the plurality of sides.
 5. A method according to claim 4 , wherein said bracing includes bracing the advancing machine between a roof and a floor of said mine opening.
 6. A method according to claim 4 , wherein said bracing includes bracing the advancing machine between walls of said mine opening.
 7. A method of retrieving a mining machine including an advancing machine, comprising: bracing the advancing machine within a mine opening; moving the mining machine toward the advancing machine; releasing the advancing machine; and moving the advancing machine away from the mining machine.
 8. A method according to claim 7 , wherein said bracing includes bracing the advancing machine between a roof and a floor of said mine opening.
 9. A method according to claim 7 , wherein said bracing includes bracing the advancing machine between walls of said mine opening.
 10. An apparatus for advancing and steering a mining machine, comprising: an advancing machine; a brace coupled to said advancing machine and being extendable to brace said advancing machine within a mine opening; and an extender operatively coupled between said advancing machine and the mining machine and capable of extension and retraction.
 11. An apparatus according to claim 10 , further comprising a second extender operatively coupled between said advancing machine and the mining machine and capable of extension and retraction.
 12. An apparatus according to claim 10 , wherein said brace comprises a hydraulic cylinder.
 13. An apparatus according to claim 10 , wherein said extender comprises a hydraulic cylinder.
 14. An apparatus according to claim 10 , wherein said brace and said extender comprise electrical actuators.
 15. An apparatus according to claim 10 , wherein said brace is extendable to brace said advancing machine between a roof and a floor of said mine opening.
 16. An apparatus according to claim 10 , wherein said brace is extendable to brace said advancing machine between walls of said mine opening.
 17. A method of navigating a mining machine including an advancing machine, comprising: bracing the advancing machine within a mine opening; bracing the mining machine within said mine opening; determining a first relative position of the advancing machine and the mining machine; releasing the mining machine; moving the mining machine away from the advancing machine; bracing the mining machine; determining a second relative position of the advancing machine and the mining machine; releasing the advancing machine; and moving the advancing machine toward the mining machine.
 18. A method according to claim 17 , wherein said determining of relative positions includes measuring at least two variable dimensions between the advancing machine and the mining machine.
 19. An apparatus for navigating a mining machine comprising: an advancing machine; a first brace coupled to said advancing machine and being extendable to brace said advancing machine within a mine opening; an extender operatively coupled between said advancing machine and the mining machine and capable of extension and retraction; and a distance measurer operatively coupled to measure at least two dimensions between the mining machine and said advancing machine.
 20. An apparatus according to claim 19 , further comprising a second brace coupled to the mining machine and being extendable to brace the mining machine within said mine opening.
 21. An apparatus according to claim 20 , wherein said distance measurer comprises a rotary potentiometer.
 22. An apparatus according to claim 20 , wherein said distance measurer comprises a linear potentiometer.
 23. An apparatus according to claim 20 , wherein said distance measurer is an integral part of said advancing machine.
 24. An apparatus according to claim 20 , wherein said extender comprises an electrical actuator.
 25. An apparatus according to claim 20 , wherein said extender comprises a hydraulic or pneumatic cylinder.
 26. A method of conveying material from a remote mining machine having a longitudinal axis using conveying units, each unit having a traction element, comprising: assembling at least some of the conveying units into a conveying assembly; and engaging at least some of the traction elements of the conveying units of said conveying assembly to move said conveying assembly.
 27. A method according to claim 26 , wherein said engaging includes providing a driving force to each of the conveying units of said conveying assembly.
 28. A method according to claim 27 , wherein said providing includes providing a synchronized driving force to each of the conveying units of said conveying assembly.
 29. A method according to claim 26 , wherein said assembling includes connecting the conveying units of said conveying assembly to substantially prevent rotation between adjacent conveying units about the longitudinal axis.
 30. An apparatus for conveying material from a remote mining machine having a longitudinal axis, comprising: a conveying assembly comprising a plurality of conveying units; and a connector coupling adjacent ones of said conveying units so as to substantially prevent rotation between said adjacent conveying units about the longitudinal axis.
 31. An apparatus according to claim 30 , wherein at least some of said conveying units include a propelling device.
 32. An apparatus according to claim 31 wherein said propelling device comprises powered wheels.
 33. An apparatus according to claim 31 , further comprising at least one common drive shaft operatively coupled to said propelling device.
 34. An apparatus according to claim 33 , wherein a plurality of said conveying units include a propelling device and said at least one common drive shaft is operatively coupled to each of said propelling devices.
 35. An apparatus according to claim 33 , further comprising a power unit located at a discharge end of said conveying assembly operatively coupled to drive said at least one common drive shaft.
 36. An apparatus according to claim 33 , further comprising a power unit located at a feed end of said conveying assembly operatively coupled to drive said at least one common drive shaft.
 37. An apparatus according to claim 33 , further comprising a power unit located at a discharge end of said conveying assembly and a power unit located at a feed end of said conveying assembly, said power units being operatively coupled to drive said at least one common drive shaft.
 38. An apparatus according to claim 30 , wherein said connector comprises: a pin on a first conveying unit of said adjacent conveying units; a fork positioned on a second conveying unit of said adjacent conveying units, said fork able to engage and disengage said pin; and a hook movably positioned on either said first or said second conveying unit and having a first position, in which said hook couples said adjacent conveying units, while allowing limited relative motion between said adjacent conveying units about an axis substantially perpendicular to the longitudinal axis, and a second position, in which said hook does not couple said adjacent conveying units.
 39. An apparatus according to claim 38 , wherein said fork has an opening with a size greater than a size of said pin for allowing a limited relative motion between said adjacent conveying units the longitudinal axis.
 40. An apparatus according to claim 38 , further comprising a spring operatively connected to bias the position of said hook. 